Method and apparatus for displaying progressive material on an interlaced device

ABSTRACT

A method and apparatus are provided for displaying progressive material on an interlaced display where the number of lines of the source frame is equal to or less than the number of lines in a display field, where such lines in the display field are derived from all of the lines of the source frame.

FIELD OF THE INVENTION

The present invention relates to interlacing methods, and moreparticularly to improving interlacing in a graphics pipeline.

BACKGROUND OF THE INVENTION

Computer displays and televisions are known to utilize different displaytechniques; computer displays utilize a progressive non-interlaceddisplay technique, while televisions utilize an interlaced technique.The progressive display technique creates frames for displaying whereineach frame includes complete pixel information for the display. Forexample, if the computer display is a 640×480 pixel display, each lineof a frame would include the appropriate pixel information for display.Thus, each frame display, which is done at a refresh rate of thecomputer display (e.g., 60 hertz, 75 hertz, 90 hertz, etc.), iscomplete. Because each frame contains complete pixel information, nohuman perception filtering is required.

The interlaced technique has two types of fields: top fields and bottomfields. Top fields and bottom fields are also known as odd and evenfields. A top field contains only the pixel information for odd lines ofthe frame, while the bottom field contains only pixel information foreven lines of the frame. As such, both fields are incomplete. Whendisplayed at the refresh rate of the television, which may beapproximately 60 hertz in North America, the fields are presented at arate of 30 top fields and 30 bottom fields per second. Because theinterlaced display technique alternates between top fields and bottomfields, the human visual process filters the fields such that completeimages (i.e. frames) are perceived by the viewer.

Prior Art FIG. 1 illustrates the manner 100 in which the interlacedtechnique operates. Initially, pixel information for a plurality ofsource lines S₀, S₁, S₂, S₃, etc. of a source frame 101 is provided.From the source lines, a top field 102 of lines T₀, T₁, T₂, T₃, etc. isextracted along with a bottom field 104 of lines B₀, B₁, B₂, B₃, etc.for display on a destination frame 103.

As shown in Prior Art FIG. 1, T₀ and T₃ are copies of S₀ and S₂.Further, scaling is done to generate T₁ and T₂ from S₀ and S₂. Suchscaling is accomplished by interpolation utilizing the equations shown.It should be noted that scaling is often used when it is desired todisplay a first number of source lines on a destination frame with asecond number of lines greater than the first number. Similar to the topfield 102, the scaling operation may also be performed on the bottomfield 104.

With the source lines S₀, S₁, S₂, S₃, etc. scaled and the top fieldlines T₀, T₁, T₂, T₃, etc. and bottom field lines B₀, B₁, B₂, B₃, etc.generated, the top and bottom fields are adapted to be depicted in adestination frame 103 on an output device 106.

As set forth in FIG. 1, a raster scanout pattern of a destination frame103 is shown to contain both top and bottom fields and a verticalblanking region. In particular, the top field lines T₀, T₁, T₂, T₃, etc.and bottom field lines B₀, B₁, B₂, B₃, etc. are projected on thedestination frame 103 in accordance with sync waveforms 108. Suchcorresponding horizontal and vertical sync waveforms 108 are shown witha vertical blanking waveform 109, to show where the active lines are inthe fields.

Table #1 illustrates various parameters used for the displayconfiguration shown in FIG. 1.

Table #1

-   -   TOTAL LINES IN DISPLAY FRAME: 13 (ODD NUMBER)    -   TOTAL LINES IN DISPLAY FIELD: 6.5    -   ACTIVE LINES IN DISPLAY FRAME: 8    -   ACTIVE LINES IN DISPLAY FIELD: 4    -   LINES IN BLANKING PERIOD: 3

Unfortunately, if flicker filtering is not employed, interlacing resultsin aliasing which is different in the two fields. This results inflickering.

Prior Art FIG. 1A illustrates an alternate technique 110 for generatingthe active lines of FIG. 1 from a source frame. In such alternatetechnique, scaling precedes interlacing, unlike the embodiment ofFIG. 1. Unfortunately, a filter used to reconstruct the new lines priorto interlacing is typically a poor anti-aliasing filter. Subsequently,the interlacing results in aliasing, which is different in the twofields, resulting again in flicker.

During both techniques for generating active lines from a source frame(FIGS. 1 and 1A), the source frame can unfortunately only be changedonce every two field scanout periods, if all of the information in thesource frame is to be displayed since the source frame is used togenerate both display fields. This restricts the frame animation rate toone half of the field display rate.

It should be noted that it is still possible to animate the sourceframes at a field scanout rate. To accomplish this, the top or bottomlines may be extracted as appropriate, as shown in the foregoingfigures. The problem, however, is that only half the source frameinformation gets displayed.

DISCLOSURE OF THE INVENTION

A method and apparatus are provided for displaying progressive materialon an interlaced display where the number of lines of the source frameis equal to or less than the number of lines in a display field (i.e.top field or bottom field) of a destination frame, where such lines inthe display field are derived from all of the lines of the source frame.

The present technique may be viewed and termed in various ways. Forexample, another method and apparatus are also provided for use duringgraphics processing. Initially, a source frame is identified including aplurality of lines. Then, a top field of a destination frame ispopulated with the lines, and a bottom field of the destination frame ispopulated with the lines. Such lines populating the top field and thebottom field are the same.

In terms of another example, a method and apparatus are provided where asource frame is initially provided including a plurality of lines. A topfield of a destination frame of an output device is then populated withboth the top lines and the bottom lines. Moreover, a bottom field of thedestination frame is populated with both the top lines and the bottomlines.

As an option, the source frame may be scaled. Such scaling producesadditional lines that are each utilized to populate the fields of thedestination frame.

In one embodiment, the output device may include a high-definitiontelevision. As an option, the lines may be sent to a digital-to-analogconverter to populate the fields of the destination frame. Syncwaveforms may also be sent to the digital-to-analog converter forpopulating the fields of the destination frame. It should be noted thatthe lines, and the sync waveforms may also be sent directly to adestination frame capable of handling such information.

These and other advantages of the present invention will become apparentupon reading the following detailed description and studying the variousfigures of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects and advantages are better understoodfrom the following detailed description of a preferred embodiment of theinvention with reference to the drawings, in which:

Prior Art FIG. 1 illustrates the manner in which the interlacedtechnique operates.

Prior Art FIG. 1A illustrates an alternate technique for generating theactive lines of FIG. 1 from a source frame.

FIG. 2 illustrates a schematic diagram showing an exemplaryarchitecture, in accordance with one embodiment.

FIG. 3 illustrates an interlacing method for use during graphicsprocessing, in accordance with one embodiment.

FIG. 4 illustrates an example of the method set forth in FIG. 3.

FIG. 4A illustrates an alternate technique for generating the activelines of FIG. 4 from a source frame.

FIG. 5 illustrates a schematic diagram showing an exemplaryarchitecture, in accordance with another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates the prior art. FIG. 2 illustrates a schematic diagramshowing an exemplary architecture 200, in accordance with oneembodiment. As shown, a frame buffer 202 is provided for storing sourceframes. As is well known, such source frames may be the product of agraphics pipeline of a progressive display system. Further, the graphicspipeline may be equipped with transform, lighting, and/or renderingcapabilities. It should be noted, however, that the source frames may beproduced in any desired manner.

Coupled to the frame buffer 202 is a display engine 204. Such displayengine 204 is capable of reading the source frames from the frame buffer202. The source frames include a plurality of lines. As an option, thedisplay engine 204 may further be capable of scaling the source framesto increase or decrease the number of lines. This technique is oftenuseful when attempting to fit source frames of a first size on a displayequipped to depict images of a second size.

The display engine 204 thus makes available a plurality of lines foroutput to a subsequent device. Such lines originate from the sourceframes and can be manipulated, i.e. scaled, in any desired manner.

In the context of the present invention, the source frame may includeany derivation of the source frames, component of the source frames, thesource frames themselves, or any other related information capable ofbeing displayed. Moreover, the lines may include top and bottom lineswhich refer to any two subsets of lines associated with the sourceframe. For example, such top and bottom lines may refer to even and oddlines. In other words, the top and bottom lines include all (or at leasta majority) of the lines of the associated source frame.

Associated with the display engine 204 is a timing generator thatcontrols the output of the lines. In particular, the timing generatorproduces control signals in the form of sync waveforms that indicatewhen the particular lines should be output. As shown in FIG. 2, thedisplay engine 204 outputs such control signals along with a stream ofpixels indicative of the top and bottom lines.

Coupled to the display engine 204 is an output device 206. Such outputdevice 206 may include a display device such as a television,high-definition television (HDTV), or any other device capable ofreceiving or displaying an output frame or field. Moreover, the outputdevice 206 may include an analog-to-digital (A/D) converter. It shouldbe noted that such A/D converter may be a stand alone device orincorporated in a display device.

FIG. 3 illustrates an interlacing method 300 for use during graphicsprocessing, in accordance with one embodiment. As an option, the method300 may be implemented in the context of the architecture 200 of FIG. 2.Of course, however, the present method 300 may be implemented in thecontext of any desired architecture. For example, the specificarchitecture of FIG. 5 may be utilized, and so on.

As shown in FIG. 3, a source frame is initially received in operation302. As mentioned earlier, the source frame may be received from a framebuffer 202, or any desired source. Utilizing the display engine 204 or asimilar device, a plurality of lines (i.e. top and bottom lines) areidentified from the source frame. Note operation 304.

Next, in operation 306, the lines are scaled. In a case where the linesare scaled to include additional lines, interpolation may be used togenerate the additional lines via “upscaling.” Such interpolation isthus useful when attempting to fit a source frame of a small size on adisplay equipped to depict images of a larger size.

In operation 308, the lines are outputted for being displayed in a topfield of a destination frame of a display. Such destination frame mayinclude any processed and/or outputted frame.

In a similar manner, another (i.e., a second) source frame may beretrieved in operation 310, and all of the lines (i.e. top and bottom)may again be identified and scaled in operations 312 and 314. Thus, thelines are outputted for being displayed in a bottom field of adestination frame of the display. Note operation 316.

During operations 304 and 312, it is important (to get the full benefitof the technique) that the number of lines of the source frame that areidentified and used is equal to or less than the number of lines in adisplay field (i.e. top field or bottom field) associated with thedestination frame of the output device. Moreover, such lines in thedisplay field are derived from (i.e. based at least in part on) all ofthe lines of the source frame. In other words, all of the lines of thesource frame are used when generating the lines in the display field. Apictorial example will be set forth during reference to FIG. 4 whichwill further illustrate this feature.

By this method 300, the source frame is inherently upscaled by a factorof two (2). This is of particular benefit when the source frames have aresolution that is much less than the resolution of a destination frameof the output device. Further, flickering and aliasing are eliminated.More advantages will be set forth hereinafter in greater detail.

In another embodiment, the top field of the destination frame ispopulated with certain lines from the source frame, and the bottom fieldof the destination frame is populated with the same lines in operations308 and 316. In other words, the lines identified, scaled and used topopulate both of the fields in operations 304–308, and 312–316 are thesame.

In still another embodiment, both the top and bottom field of thedestination frame may be populated with both the top and bottom linesor, in other words, all of the lines of the source frame. This is thecase, for example, if the source frame is not changed for two fieldscanout periods. It should be noted that the top and bottom lines referto any two subsets of lines associated with the source frame. Forexample, such top and bottom lines may refer to even and odd lines. Inother words, the top and bottom lines include all (or at least amajority) of the lines of the associated source frame.

FIG. 4 illustrates an example 400 of the method 300 set forth in FIG. 3.Initially, pixel information for a plurality of source lines S₀, S₁, S₂,S₃, etc. of a source frame is received, as indicated in operations 302and 310. From the source lines S₀, S₁, S₂, S₃, etc., top lines T₀, T₁,T₂, T₃, etc. are extracted along with bottom lines B₀, B₁, B₂, B₃, etc.

Again, it is important (to get the full benefit of the technique) thatthe number of lines of the source frame that are identified and used isequal to or less than the number of lines in a display field (i.e. topfield or bottom field) associated with the destination frame of theoutput device. Moreover, such lines in the display field are derivedfrom all of the lines of the source frame. Of course, this technique maybe termed in various other ways set forth hereinabove. It is possible toapply this technique where the number of source frame lines is less thanthe number of displayed field lines but it may require downscaling ofthe source frame vertically which results in a loss of information. Thistechnique provides the benefit of removing flicker.

With the top lines T₀, T₁, T₂, T₃, etc. and bottom lines B₀, B₁, B₂, B₃,etc. generated, the top and bottom lines are ready to be depicted on adestination frame 403 of an output device 406. In use, the top fieldlines T₀, T₁, T₂, T₃, etc. and bottom field lines B₀, B₁, B₂, B₃, etc.are projected on the destination frame 403 in accordance with horizontaland vertical sync waveforms 408 as well as a vertical blanking waveform410, to show where the active lines are in the fields.

FIG. 4A illustrates an alternate technique 411 for generating the activelines of FIG. 4 from the source frame. As shown in FIG. 4A, T₀ and T₃are copies of S₀ and S₂. Further, scaling is done to generate T₁ and T₂from S₀–S₂. Such scaling is accomplished by interpolation utilizing theequations shown. Similar to the top lines T₀, T₁, T₂, T₃, etc., thescaling operation may also be performed on the bottom lines B₀, B₁, B₂,B₃, etc. Note operations 306 and 314 of FIG. 3.

By this design, the source frame is vertically upscaled by a factor of4/3 by the foregoing process. Further, flickering and aliasing areeliminated since the present technique is not affected by movementdifferences between the top and bottom fields of the source frame,because the whole source frame is sent to the display device at once. Noflicker filtering is thus required. Still yet, the present systemappears to be a progressive display to software and other systems. Yetanother advantage involves the capability of animating at the fieldscanout rate, without the loss of any information.

FIG. 5 illustrates a schematic diagram showing an exemplary architecture500, in accordance with another embodiment. As shown, a frame buffer 502is provided for storing source frames. Coupled to the frame buffer 502is a cathode ray tube controller (CRTC) 504 for reading the sourceframes therefrom.

Also included is a high definition television (HDTV) scaler 506 coupledto the CRTC 504. Such HDTV scaler 506 is capable of scaling the sourceframes to increase the number of top and bottom lines. This technique isnecessary to fit the source frames in HDTV format. In one example, thepresent embodiment may be used to upscale a 640×480 source frame to besuitable for display on a destination field with dimensions of 1920×540.

Associated with the HDTV scaler 506 is a timing generator 507 thatcontrols the output of the top and bottom lines. In particular, thetiming generator produces control signals in the form of sync waveformsthat indicate when the particular lines should be outputted.

As shown in FIG. 5, the timing generator 507 outputs such controlsignals along with image information to an analog-to-digital (A/D)converter 508. The A/D converter 508 converts the image information toan analog format suitable for being displayed using a HDTV 510 coupledto the A/D converter 508.

While various embodiments have been described above, it may beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment maynot be limited by any of the above described exemplary embodiments, butmay be defined only in accordance with the following claims and theirequivalents.

1. An interlacing method for use during graphics processing, comprising;(a) identifying a source frame including a plurality of top lines and aplurality of bottom lines; and (b) populating each of a top field and abottom field of a destination frame of an output device with both thetop lines and the bottom lines, such that the lines populating the topfield and the bottom field of the destination frame are the same;wherein the number of lines of each source frame is equal to or lessthan the number of lines of the corresponding display field of thedestination frame.
 2. The method as recited in claim 1, wherein thesource frame is inherently upscaled by a factor of two (2).
 3. Themethod as recited in claim 1, wherein flickering is eliminated.
 4. Themethod as recited in claim 1, and further comprising prior toidentifying the source frame, scaling the source frame.
 5. The method asrecited in claim 1, wherein the output device includes a high-definitiontelevision.
 6. The method as recited in claim 1, and further comprisingsending the top lines and the bottom lines to a digital-to-analogconverter to populate the top field of the destination frame.
 7. Themethod as recited in claim 6, and further comprising sending the toplines and the bottom lines to the digital-to-analog converter topopulate the bottom field of the destination frame.
 8. The method asrecited in claim 7, and further comprising sending sync waveforms to thedigital-to-analog converter for populating the top field and the bottomfield of the destination frame each with both the top lines and thebottom lines.
 9. An apparatus producing interlaced output, comprising;(a) logic for identifying a source frame including a plurality of toplines and a plurality of bottom lines; and (b) logic for populating eachof a top field and a bottom field of a destination frame of an outputdevice with both the top lines and the bottom lines, such that the linespopulating the top field and the bottom field of the destination frameare the same; wherein the number of lines of each source frame is equalto or less than the number of lines of the corresponding display fieldof the destination frame.
 10. The apparatus as recited in claim 9,wherein the source frame is inherently upscaled by a factor of two (2).11. The apparatus as recited in claim 9, wherein flickering iseliminated.
 12. The apparatus recited in claim 9, and further comprisinglogic for scaling the source frame.
 13. The apparatus as recited inclaim 9, wherein the output device includes a high-definitiontelevision.
 14. The apparatus as recited in claim 9, and furthercomprising logic for sending the top lines and the bottom lines to adigital-to-analog converter to populate the top field of the destinationframe.
 15. The apparatus as recited in claim 14, and further comprisinglogic for sending the top lines and the bottom lines to thedigital-to-analog converter to populate the bottom field of thedestination frame.
 16. The apparatus as recited in claim 15, and furthercomprising logic for sending sync waveforms to the digital-to-analogconverter for populating the top field and the bottom field of thedestination frame each with both the top lines and the bottom lines. 17.An apparatus for producing interlaced output, comprising; (a) a framebuffer for storing a source frame including a plurality of top lines anda plurality of bottom lines; and (b) a display engine coupled to theframe buffer, the display engine adapted for populating each of a topfield and a bottom field of a destination frame of an output device withboth the top lines and the bottom lines, such that the lines populatingthe top field and the bottom field of the destination frame are thesame; wherein the total number of lines of each source frame is equal toor less than the number of lines of the corresponding display field ofthe destination frame.
 18. The apparatus as recited in claim 17, whereinthe source frame is inherently upscaled by a factor of two (2).
 19. Theapparatus as recited in claim 17, wherein flickering is eliminated. 20.The apparatus as recited in claim 17, wherein the source frame isscaled.
 21. The apparatus as recited in claim 17, wherein the outputdevice includes a high-definition television.
 22. The apparatus asrecited in claim 17, wherein the top lines and the bottom lines are sentto a digital-to-analog converter to populate the top field of thedestination frame.
 23. The apparatus as recited in claim 22, wherein thetop lines and the bottom lines are sent to the digital-to-analogconverter to populate the bottom field of the destination frame.
 24. Theapparatus as recited in claim 23, wherein sync waveforms are sent to thedigital-to-analog converter for populating the top field and the bottomfield of the destination frame each with both the top lines and thebottom lines.
 25. An apparatus for producing interlaced output for useduring graphics processing, comprising; (a) means for identifying asource frame including a plurality of top lines and a plurality ofbottom lines; and (b) means for populating each of a top field and abottom field of a destination frame of an output device with both thetop lines and the bottom lines, such that the lines populating the topfield and the bottom field of the destination frame are the same;wherein the number of lines of each source frame is equal to or lessthan the number of lines of the corresponding display field of thedestination frame.
 26. An interlacing method for use during graphicsprocessing, comprising; (a) receiving a first source frame; (b)identifying a plurality of lines from the first source frame; (c)scaling the lines from the first source frame; (d) outputting the linesfrom the first source frame for being displayed in a top display fieldof a destination frame; (e) receiving a second source frame; (f)identifying a plurality of lines from the second source frame; (g)scaling the lines from the second source frame; and (h) outputting thelines from the second source frame for being displayed in a bottomdisplay field of the destination frame; (i) wherein the number of linesof each source frame is equal to or less than the number of lines of thecorresponding display field of the destination frame, and the lines ofthe corresponding display field of the destination frame are derivedfrom all of the lines of the associated source frame, and the linespopulating the top field and the bottom field are the same.